In air conditioning systems (both heating and cooling) there is usually a need for proportion of fresh air flow, and sometimes for total flow of fresh outside air to be supplied to the conditioned space for ventilation purposes. This is wasteful of energy, and requires the use of larger equipment than is otherwise necessary if an efficient heat exchanger is employed. Also in evaporative air cooling, an objection has been raised against the high humidity which exists when the "conditioned" air contains the moisture of evaporation. To overcome these difficulties it has been proposed to utilise a plurality of parallel spaced plates of imperforate material arranged as a stack, there being closure means between the edges of adjacent plates, the closure means between any pair of adjacent plates being along opposite edges and the closure means between the next pair of adjacent plates also being along opposite but alternate edges, thereby dividing the stack into two multi-cavity conduits, and reference is made to Australian Pat. No. 425,702 standing in the name of Commonwealth Scientific and Industrail Research Organisation. In the waste heat application the incoming fresh air is heated by the exhausting air on one side of the plates of the stack while in the evaporative cooling application, the incoming fresh air is indirectly cooled by evaporatively cooled exhaust air on the other side of the plates of the stack.
One of the difficulties which has been encountered with previous stacks has been the difficulty of joining of the edges of the plates to form the required two conduits. Full sealing by welding is difficult to achieve, and use of adhesives is tedious and often unsatisfactory.
The main objects of this invention are to provide improvements whereby a heat transfer pack is formed simply and at low cost, wherein the spaces between the plates are maintained, and wherein an acceptable "seal" between the two conduits is achieved without welding or adhering the plates or without the use of a separate sealing medium between the plates.